490 
OBSERVATIONS ON THE 
by regarding the fresh water species of Hydrje, which are 
very simple animals, as the type of the group which in- 
cludes the Sertularia, rest satisfied, that all that is singular 
in their construction, has been detected by the acuteness 
of Ellis, and thus neglect a field of investigation, not more 
rich in elegant forms, than in variety of structure ai^d func- 
tion. 
I may add, that the Sertularia cuscuta and aS'. uva agree 
in the remarkable character of having only eight tentaciila^ 
and in the ovate subsessile denticles. The former is placed 
by M. Lamouroux in his genus Sertularia, while the lat- 
ter forms a part of a very motley group, which he terms 
Clytia. Neither of these species, however, can be con- 
sidered as belonging to the genera in which they are classed, 
since they differ from the characters by which these genera 
are distinguished. It is my intention, in a synopsis of 
British animals which I am engaged in preparing for the 
press, to constitute these two species into a new genus, and 
by naming it Walkeeia, consecrate it to the memory of 
the late Dr Walker, Professor of Natural History in the 
University of Edinburgh. Known, as he was, to several 
members of the Wernerian Society, as profoundly versed 
in all the departments of natural history, and extolled as 
he has been, in the sketch of his life which has been com- 
municated to the Society by his meritorious successor, the 
present compliment to his name may be deemed insigni- 
ficant. Perhaps it is so ; but I have been led to pay it, 
from having had an opportunity of judging of his intimate 
acquaintance with the tribe of zoophytes to which this 
group belongs, by inspecting a collection of specimens of 
various species of Sertularia?, which he had collected on 
the Scottish shores, and arranged and named. These have 
exhibited numerous proofs of his zeal, his knowledge, and 
his sagacity. 
